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Use IO#seek when possible #144

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Merged
byroot merged 1 commit into from
May 20, 2026
Merged

Use IO#seek when possible #144

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17 changes: 14 additions & 3 deletions lib/marcel/magic.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -128,11 +128,11 @@ def self.magic_match_io(io, matches, buffer)
if value.is_a?(Regexp)
match_regex(io, offset, value, buffer)
elsif Range === offset
io.read(offset.begin, buffer)
io_seek(io, offset.begin, buffer)
x = io.read(offset.end - offset.begin + value.bytesize, buffer)
x && x.include?(value)
else
io.read(offset, buffer)
io_seek(io, offset, buffer)
io.read(value.bytesize, buffer) == value
end
end
Expand All @@ -151,6 +151,17 @@ def self.match_regex(io, offset, regexp, buffer)
data.match?(regexp)
end

private_class_method :magic_match, :magic_match_io, :match_regex
def self.io_seek(io, offset, buffer)
return if offset == 0

if io.respond_to?(:seek)
io.seek(offset, IO::SEEK_CUR)
else
# Some IOs don't support `seek`. e.g. Rack::RewindableInput
io.read(offset, buffer)
end
end

private_class_method :magic_match, :magic_match_io, :match_regex, :io_seek
end
end
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